Partial power converter-based modular UPS (Uninterrupted Power Supply) parallel operation SOC (System On Chip) equalization control method

Abstract

The invention discloses a partial power converter-based modular UPS parallel operation SOC equalization control method, and aims to solve the problem that the partial power converter-based modular UPS parallel operation lacks the SOC equalization control method, so that the charging / discharging current or power difference of a UPS backup battery is large, and local hot spots or local downtime is caused. The overall utilization rate of parallel operation of the UPS is improved, and the service life of a backup battery in the UPS is prolonged. When the MPPC-UPS adopts battery constant-current charging control, an SOCcharge equalization control scheme is adopted, and a charging current reference value is changed according to the real-time SOC change of the backup battery, so that SOC equalization of the backup battery in a charging state is realized; when the MPPC-UPS adopts load constant-voltage control, an SOCIDCharge balance control scheme is adopted, a load voltage reference value is changed according to the real-time SOC change of the backup battery, and the discharge current of the backup battery is indirectly changed so as to realize SOC balance in the discharge state of the backup battery.

Description

Technical Field

[0001] The invention relates to the technical field of UPS, and in particular to a SOC balancing control method for parallel operation of modular UPS based on partial power converters. Background Art

[0002] Parallel operation is the main operation mode of distributed UPS (uninterruptible power supply system), which can solve the problem that centralized UPS cannot cope with single point failure and has low reliability. When multiple distributed UPS are operated in parallel, the difference in the state of charge (SOC) of the backup batteries in each UPS will cause the battery charging / discharging current or power to be different. Some of the backup batteries may be overcharged or deeply discharged, which will not only shorten the overall service life of the UPS, but in serious cases, may even cause fires due to the emergence of local hot spots, affecting the safe operation of the data center. In addition, due to the difference in SOC, during the period when the backup battery discharges to provide uninterrupted power supply to the load, the battery with a lower state of charge may reach the discharge limit after a short period of discharge, forcing the local load to shut down, reducing the available capacity and utilization rate of the backup battery of the UPS as a whole, which is not conducive to the overall power supply reliability of the data center system. Therefore, it is necessary to coordinate the control of the distributed UPS operating in parallel to achieve balanced management of the state of charge of the backup batteries in multiple UPS.

[0003] The existing SOC balancing control of traditional UPS is aimed at conventional full-power converter UPS, and the traditional droop control method is often used. When facing a small-capacity system, the voltage stabilization effect is good, but the traditional droop control has two disadvantages: large output current balance deviation and DC voltage drop, which makes the adaptability and accuracy of SOC value balancing poor. On the basis of droop control, related research at home and abroad has proposed SOC balancing control methods based on power functions, exponential functions, hyperbolic functions and other complex functions, but these methods are also applicable to conventional full-power converter UPS. For modularized partial power converter based UPS (MPPC-UPS), there is still a lack of SOC balancing control methods under parallel operation. The SOC balancing control of modular UPS based on partial power converters will become one of the important factors affecting its further promotion and application. Summary of the invention

[0004] In order to solve the problem that there is still a lack of SOC balancing control method for parallel operation of modular UPS based on partial power converters, which may lead to large differences in charging / discharging current or power of UPS backup batteries, resulting in local hot spots or local downtime, the present invention provides a SOC balancing control method for parallel operation of modular UPS based on partial power converters in view of the shortcomings of the prior art.

[0005] The present invention is achieved by adopting the following technical solutions:

[0006] A SOC balancing control method for parallel operation of modular UPS based on partial power converters is disclosed. The modular UPS based on partial power converters is denoted as MPPC-UPS, and has k MPPC-UPS modules connected in parallel to a common DC bus. The DC ICT loads in the MPPC-UPS modules are different in size, and the charge states of the backup batteries are different. All the backup batteries have the same structure. The control method includes the following two parts:

[0007] (1) SOC balancing control under battery constant current charging control (in grid-connected mode): The control goal is to achieve SOC balancing between the batteries of each parallel MPPC-UPS module during grid-connected operation;

[0008] The actual SOC of the battery in the MPPC-UPS module j Value to calculate the battery charging current reference value The expression is:

[0009]

[0010] Where: I mbat,max Indicates the maximum charging current allowed for the battery in the MPPC-UPS module; K SOC,c Indicates the SOC balance coefficient under constant current charging control of the battery; SOC min and SOC max They represent the lower and upper limits of the SOC allowed during battery operation, which are the same for all batteries; j is an integer from 1 to k, where k is an integer greater than 1;

[0011] The SOC balancing coefficient under the constant current charging control of the battery is:

[0012]

[0013] Set the battery charging current reference value Substitute it into the battery constant current charging control of the MPPC-UPS module to achieve the balance of battery SOC in multiple parallel MPPC-UPS modules;

[0014] (2) SOC balancing control under load constant voltage control (in off-grid mode): Its control goal is to achieve SOC balancing between the batteries of each parallel MPPC-UPS module in off-grid mode;

[0015] According to the actual SOC of the battery in the MPPC-UPS module j Value to calculate the load voltage reference value The expression is:

[0016]

[0017] Where: V mload,min and V mload,max They represent the minimum and maximum values ​​allowed for the load voltage in the MPPC-UPS module; K SOC,v Indicates the SOC balance coefficient under load constant voltage control;

[0018] The SOC balancing coefficient under the load constant voltage control is:

[0019]

[0020] Set the load voltage reference value Substitute it into the load constant voltage control of the MPPC-UPS module to achieve the balance of battery SOC in multiple parallel MPPC-UPS modules.

[0021] Furthermore, the expression of battery constant current charging control is:

[0022]

[0023] Where: I mload is the actual value of DC load current; I dif,ref is the reference value of the horizontal branch current of the T node; I dif is the actual value of the lateral branch current at the T node; D mc,ref k is the phase shift duty ratio reference value of the dual active full-bridge DC / DC converter; mc,pj , k mc,ij They are proportional integral controller PI for constant current charging control of batteries mc The proportional coefficient and integral coefficient of ; s is the Laplace operator;

[0024] The expression of load constant voltage control is:

[0025]

[0026] Where: D mv,refj represents the phase shift duty cycle reference value of the jth MPPC-UPS module, V m1,j represents the actual voltage value of the port where the j-th MPPC-UPS module is connected to the load, k mv,pj and k mv,ij They respectively represent the proportional coefficient and integral coefficient of the load constant voltage control of the j-th MPPC-UPS module.

[0027] Furthermore, the MPPC-UPS module includes a partial power converter, a backup battery, and a DC load, wherein the partial power converter is composed of a dual active full-bridge DC / DC converter, an inductor L m1 and inductor L m2The dual active full-bridge DC / DC converter consists of a full-bridge FB m1 、Full bridge FB m2 And high frequency isolation transformer;

[0028] The positive pole of the DC bus passes through the inductor L m1 Connect the positive pole of the DC load, the negative pole of the DC load is connected to the positive pole of the backup battery, the connection point between the negative pole of the DC load and the positive pole of the backup battery is recorded as the T node, the negative pole of the backup battery is connected to the negative pole of the DC bus; the positive pole of the DC bus passes through the inductor L m1 Connect full bridge FB m1 Positive, full bridge FB m1 The negative pole passes through the inductor L m2 Connected to the T node to form a DC bus, inductor L m1 、Full bridge FB m1 、Inductance L m2 The branch connected in series with the backup battery, at the same time the full bridge FB m1 It also forms a parallel connection relationship with the DC load; full bridge FB m2 The positive electrode passes through the inductor L m2 Connect to the T node, and its negative terminal is connected to the negative terminal of the backup battery.

[0029] Compared with the prior art, the SOC balancing control method for parallel operation of modular UPS based on partial power converters provided by the present invention has the following advantages and positive effects:

[0030] (1) It fills the technical gap of SOC balancing control method under parallel operation of modular UPS based on partial power converters, and can realize balanced management of backup batteries in UPS parallel operation system, avoiding the occurrence of local hot spots or local downtime caused by large differences in backup battery charge / discharge current or power, promoting the improvement of the overall utilization rate of all parallel MPPC-UPS and extending the service life of backup batteries;

[0031] (2) The implementation is simple and reliable. Each MPPC-UPS parallel module can achieve balancing by collecting local information, without the need for communication between MPPC-UPS parallel modules.

[0032] (3) Different balancing control methods are used in the battery constant current charging control and load constant voltage control of the MPPC-UPS. Different balancing methods are used in different operating modes, and the adaptability to multi-operating conditions is strong;

[0033] (4) When there are errors in the battery SOC calculation in different modules, it will only affect the battery charging / discharging rate and the length of the SOC balancing time, but will not affect the accuracy of SOC balancing, which is beneficial to improving the overall power supply reliability of the data center system and the utilization rate of the backup battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The topological structure diagram of a modular UPS based on partial power converters operating in parallel according to the present invention.

[0035] Figure 2 This is the SOC balancing control scheme diagram under MPPC-UPS battery constant current charging control.

[0036] Figure 3 The charging current reference value under constant current charging control of the battery changes with SOC j Schematic diagram of the changes.

[0037] Figure 4 This is the SOC balancing control scheme diagram under MPPC-UPS load constant voltage control.

[0038] Figure 5 The load voltage reference value under load constant voltage control changes with SOC j Schematic diagram of the changes.

[0039] Figure 6 This is the experimental waveform of SOC balancing of backup battery of MPPC-UPS parallel system in grid-connected mode.

[0040] Figure 7 This is the experimental waveform of the backup battery SOC balancing test of the MPPC-UPS parallel system in off-grid mode. DETAILED DESCRIPTION

[0041] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0042] like Figure 1 As shown, it is the system structure of MPPC-UPS in parallel operation, with a total of k MPPC-UPS modules connected in parallel to a common DC bus. The DC ICT (information and communications technology) load in each MPPC-UPS module is different in size. The characteristic of the ICT load is a controlled current source with a variable resistance, and the backup battery SOC is also different. SOC is a parameter whose value changes in real time. The structure of each backup battery is the same. In order to be able to describe it more clearly in the following text, two parallel MPPC-UPS modules numbered v and w are used as an example. The common DC bus voltage of the parallel MPPC-UPS modules is V mdc ;MPPC-UPS v The voltage and current variables in the module are denoted by v, and the state of charge of the backup battery is denoted by SOC v ;MPPC-UPS wThe voltage and current variables in the module are denoted by w, and the state of charge of the backup battery is denoted by SOC w .

[0043] The MPPC-UPS (modular UPS based on partial power converter) module includes a partial power converter, a backup battery, and a DC load, which are compactly connected. The partial power converter consists of a dual active full-bridge DC / DC converter, an inductor L m1 and inductor L m2 Through special connection, the dual active full-bridge DC / DC converter consists of a full-bridge FB m1 、Full bridge FB m2 and a high-frequency isolation transformer. First, the DC bus positive pole passes through the inductor L m1 Connect the positive pole of the DC load, the negative pole of the DC load is connected to the positive pole of the backup battery (the connection point between the negative pole of the DC load and the positive pole of the backup battery is marked as the T node), and the negative pole of the backup battery is connected to the negative pole of the DC bus, that is, the DC bus, inductor L m1 , DC load and backup battery form a series branch. Secondly, the positive pole of the DC bus passes through the inductor L m1 Connect full bridge FB m1 Positive, full bridge FB m1 The negative pole passes through the inductor L m2 Connected to the T node to form a DC bus, inductor L m1 、Full bridge FB m1 、Inductance L m2 The branch connected in series with the backup battery, at the same time the full bridge FB m1 It also forms a parallel connection relationship with the DC load. Full bridge FB m2 The positive electrode passes through the inductor L m2 Connected to the T node, its negative terminal is connected to the negative terminal of the backup battery, that is, the full bridge FB m2 Through the inductor L m2 Connected in parallel with the backup battery to form a feedback branch. The DC busbar connected to the main power supply, the backup battery and the DC load form an uninterruptible power supply module through a partial power converter. When the main power supply is operating normally, the backup battery is charged and the load is powered through the partial power converter. When the main power supply stops operating abnormally, the backup battery provides uninterruptible power supply to the load through the partial power converter.

[0044] The SOC balancing control method for parallel operation of modular UPS based on partial power converters of the present invention is implemented by using k parallel modular UPS based on partial power converters, where k is an integer greater than 1; the method includes the following two parts:

[0045] (1) Figure 2 As shown in the figure, it is the SOC balancing control scheme under the constant current charging control of the battery, denoted as SOCcharge Balance control: Its control goal is to achieve SOC balance between parallel module batteries during grid-connected operation. v and MPPC-UPS w The module's battery constant current charging control is:

[0046]

[0047] Where: j = v or w; I mbat,refj Is the battery charging current reference value; I mload is the DC load current; I dif,ref is the reference value of the horizontal branch current of the T node; I dif is the lateral branch current at node T (i.e., the current flowing through the inductor L m2 The actual value of the current; D mc,ref k is the phase shift duty ratio reference value of the dual active full-bridge DC / DC converter; mc,p , k mc,i Proportional integral controller PI for constant current charging control of batteries mc The proportional coefficient and integral coefficient.

[0048] By changing the battery charging current reference value I mbat,refj (j = v or w) to achieve the balance of the battery SOC in the two parallel modules. Specifically, according to the actual state of charge SOC of the battery j (j = v or w) The value is calculated according to the following formula: The battery charging current reference value I mbat,refj (j = v or w); In order to avoid overcharging, it is also necessary to set the corresponding limit value, considering the battery charging current reference value of the actual battery charge state (j=v or w) is:

[0049]

[0050] Where: I mbat,max Indicates MPPC-UPS j (j = v or w) is the maximum charging current allowed by the battery. Since all batteries are homogeneous (battery homogeneity means that the battery structure, model, and battery parameters are the same, and the present invention only considers the homogeneous situation), the I mbat,max Same; K SOC,c Indicates the SOC balance coefficient under constant current charging control of the battery; SOC min and SOC max They represent the lower and upper limits of the SOC allowed during battery operation, which are the same for all batteries.

[0051] The SOC balancing coefficient under constant current charging control of the battery is:

[0052]

[0053] like Figure 3 As shown, when SOC j <SOC min When SOC is low, the maximum charging current is used to charge the battery, thereby achieving fast charging of the battery; when SOC min ≤SOC j ≤SOC max When the battery charging current will change with SOC j When the MPPC-UPS modules are connected in parallel, the battery can automatically balance the SOC. j >SOC max When the charging current is 0, charging stops to avoid overcharging the battery.

[0054] In summary, SOC charge The balancing control solution only needs to add the SOC balancing control link in addition to the battery constant current charging control, and calculate the battery charging current reference value considering the actual battery charge state according to the SOC calculation of each battery itself, without changing the underlying control of the MPPC-UPS module. charge In the balancing control scheme, each MPPC-UPS module only needs to collect its local information for control without exchanging information with other parallel MPPC-UPS modules. This is a non-communication SOC balancing control scheme that can avoid communication delays or communication failures that are not conducive to the reliable operation of the system.

[0055] (2) Figure 4 As shown in the figure, it is the SOC balance control scheme under load constant voltage control, denoted as SOC discharge Balance control: Its control goal is to achieve SOC balance between batteries of each parallel MPPC-UPS module in off-grid mode. j (j=v or w) load constant voltage control is:

[0056]

[0057] Where: D mv,refj represents the phase shift duty cycle reference value of the jth MPPC-UPS module, V mload,refj It represents the voltage reference value of the load in the jth module, that is, the ICT, V m1,j represents the actual voltage value of the port where the j-th MPPC-UPS module is connected to the load, k mv,pj and k mv,ij They respectively represent the proportional coefficient and integral coefficient of the load constant voltage control of the j-th MPPC-UPS module; s is the Laplace operator;.

[0058] The controlled variable of the load constant voltage control of the MPPC-UPS module is the load voltage, not the battery voltage or battery current. However, when the MPPC-UPS module operates in off-grid mode, the battery discharges for the load, and the load port voltage and the battery voltage will be coupled through the power balance relationship. Therefore, the load voltage reference value V mload,refj (j = v or w) indirectly realizes the SOC balance of the batteries in the two parallel MPPC-UPS modules. Specifically, according to the actual SOC of the battery j (j=v or w) value to calculate the load voltage reference value V mload,refj (j = v or w). Load voltage reference value considering the actual state of charge of the battery (j=v or w) is expressed as:

[0059]

[0060] Where: V mload,min and V mload,max Respectively represent MPPC-UPS j (j=v or w) is the minimum and maximum value allowed for the load voltage; K SOC,v Indicates the SOC balancing coefficient under load constant voltage control.

[0061] The SOC balance coefficient under load constant voltage control is:

[0062]

[0063] like Figure 5 As shown, when SOC j <SOC min When SOC is , the load voltage is controlled at the minimum value, the load power is reduced accordingly, and the battery discharge rate will also be slowed down to extend the uninterrupted power supply time; when SOC min ≤SOC j ≤SOC max When the load voltage will change with SOC j As the SOC increases, the load power will also increase linearly. j As the SOC increases, the battery discharge power will also increase with the SOC j Increases with increase, that is, SOC j The larger the battery, the faster the battery discharge rate, thus achieving the balance of battery SOC between different parallel modules; when SOC j >SOC max When the load voltage is controlled at the maximum value, the load power increases accordingly, and the battery discharge rate will also become faster.

[0064] MPPC-UPS 1 、MPPC-UPS 2 and MPPC-UPS3 The initial state of charge of the backup battery is set to 55%, 50% and 40% respectively. At t = 5min, the proposed SOC charge Balanced control scheme. The experimental waveform is as follows Figure 6 shown.

[0065] like Figure 6 As shown in (a) and (b), start SOC charge After the balanced control scheme, MPPC-UPS1, MPPC-UPS 2 and MPPC-UPS 3 SOC of the backup battery 1 , SOC 2 and SOC 3 The difference between them gradually decreases; after about 30 minutes, SOC 1 , SOC 2 and SOC 3 The difference between them is almost 0, which means that SOC 1 =SOC 2 =SOC 3 , it can be seen that the proposed SOC charge The effectiveness of the balanced control scheme. Figure 6 As shown in (c), due to the difference in initial state of charge, the MPPC-UPS 1 、MPPC-UPS 2 and MPPC-UPS 3 The initial value of the backup battery voltage is different; in the grid-connected mode, the backup battery voltage gradually increases during charging, and as the SOC 1 , SOC 2 and SOC 3 gradually become consistent, the backup battery voltage V mbat,1 、V mbat,2 and V mbat,3 Also gradually become equal. Figure 6 As shown in (d), the load voltages in the three MPPC-UPS are respectively V mload,1 =V mdc –V mbat,1 、V mload,2 =V mdc –V mbat,2 and V mload,3 =V mdc –V mbat,3 Therefore, at the same DC bus voltage V mdc As the backup battery voltage V mbat,1 、V mbat,2 and V mbat,3 tends to be consistent, the load voltage V mload,1 、Vmload,2 and V mload,3 gradually became equal. Figure 6 (e) shows the SOC charge Under the balanced control scheme, the backup battery current I mbat,1 ,I mbat,2 and I mbat,3 The trend of change is also changing. Figure 6 The backup battery charging power is shown in (g).

[0066] MPPC-UPS 1 、MPPC-UPS 2 and MPPC-UPS 3 The initial state of charge of the backup battery is set to 85%, 75% and 70% respectively. At t = 5min, the proposed SOC discharge Balanced control scheme. The experimental waveform is as follows Figure 7 shown.

[0067] like Figure 7 As shown in (a) and (b), MPPC-UPS 1 、MPPC-UPS 2 and MPPC-UPS 3 SOC of the backup battery 1 , SOC 2 and SOC 3 The difference between them gradually decreases; after about 30 minutes, SOC 1 , SOC 2 and SOC 3 The difference between them is almost 0, which means that SOC 1 =SOC 2 =SOC 3 , it can be seen that the proposed SOC discharge The effectiveness of the balanced solution. Figure 7 As shown in (c), due to the difference in initial state of charge, the MPPC-UPS 1 、MPPC-UPS 2 and MPPC-UPS 3 The initial voltage value of the backup battery is also different; in off-grid mode, the voltage of the backup battery gradually decreases during discharge, and as SOC 1 , SOC 2 and SOC 3 gradually become consistent, the backup battery voltage V mbat,1 、V mbat,2 and V mbat,3 Also gradually become equal. SOC is not started in the initial stage discharge During balanced control, the load voltage is 380V; when starting SOCdischarge After that, the load voltage reference value changes with the change of the SOC of each MPPC-UPS backup battery, and the load voltage V mload,1 、V mload,2 and V mload,3 As SOC gradually decreases, it will eventually converge to the same level, such as Figure 7 As shown in (d). Backup battery current I mbat,1 ,I mbat,2 and I mbat,3 According to the load power demand and backup battery voltage changes, such as Figure 7 As shown in (e), other changes include Figure 7 The backup battery discharge power shown in (g) (the negative sign in the figure indicates discharge) needs to meet the following requirements at all times: Figure 7 The load power demand is shown in (h).

[0068] The present invention fills the technical gap of the SOC balancing control method under the parallel operation of modular UPS based on partial power converters, can realize the balanced management of the backup battery in the UPS parallel operation system, avoids the occurrence of local hot spots or local downtime caused by large differences in the charge / discharge current or power of the backup battery, promotes the overall utilization rate of all parallel MPPC-UPS, and prolongs the service life of the backup battery; its implementation method is simple, and no communication between UPS parallel modules is required, so that the backup battery in the UPS parallel operation system can be balanced. Management. In particular, during the period when the backup battery discharges to provide uninterrupted power supply to the load in the off-grid mode, the SOC balancing control scheme can minimize the occurrence of local downtime caused by a certain MPPC-UPS reaching the discharge limit, which is conducive to improving the reliability of uninterrupted power supply; when there is an error in the battery SOC calculation in different modules, it will only affect the battery charge / discharge rate and the length of the SOC balancing time, but will not affect the accuracy of the SOC balancing, which is conducive to improving the overall power supply reliability of the data center system.

[0069] When the MPPC-UPS adopts battery constant current charging control (grid-connected mode), SOC charge The balancing control scheme changes the charging current reference value according to the real-time SOC change of the backup battery to achieve SOC balancing of the backup battery under charging state; when the MPPC-UPS adopts load constant voltage control, the SOC discharge The balancing control scheme changes the load voltage reference value according to the real-time SOC change of the backup battery, and indirectly changes the backup battery discharge current to achieve SOC balancing in the backup battery discharge state.

[0070] Any matters not described in the present invention are applicable to the prior art.

Claims

1. A SOC balancing control method for parallel operation of modular UPS based on partial power converters, characterized in that: The modular UPS based on partial power converter is denoted as MPPC-UPS, which has k MPPC-UPS modules connected in parallel to a common DC bus. The DC ICT load size in each MPPC-UPS module is different, and the charge state of the backup battery is different. The structure of all backup batteries is the same. The control method includes the following two parts: (1) SOC balancing control under battery constant current charging control (in grid-connected mode): The control goal is to achieve SOC balancing between the batteries of each parallel MPPC-UPS module during grid-connected operation; The actual SOC of the battery in the MPPC-UPS module j Value to calculate the battery charging current reference value The expression is: Where: I mbat,max Indicates the maximum charging current allowed for the battery in the MPPC-UPS module; K SOC,c Indicates the SOC balance coefficient under constant current charging control of the battery; SOC min and SOC max They represent the lower and upper limits of the SOC allowed during battery operation, which are the same for all batteries; j is an integer from 1 to k, where k is an integer greater than 1; The SOC balancing coefficient under the constant current charging control of the battery is: Set the battery charging current reference value Substitute it into the battery constant current charging control of the MPPC-UPS module to achieve the balance of battery SOC in multiple parallel MPPC-UPS modules; (2) SOC balancing control under load constant voltage control (in off-grid mode): Its control goal is to achieve SOC balancing between the batteries of each parallel MPPC-UPS module in off-grid mode; According to the actual SOC of the battery in the MPPC-UPS module j Value to calculate the load voltage reference value The expression is: Where: V mload,min and V mload,max They represent the minimum and maximum values ​​allowed for the load voltage in the MPPC-UPS module; K SOC,v Indicates the SOC balance coefficient under load constant voltage control; The SOC balancing coefficient under the load constant voltage control is: Set the load voltage reference value Substitute it into the load constant voltage control of the MPPC-UPS module to achieve the balance of battery SOC in multiple parallel MPPC-UPS modules.

2. The SOC balancing control method for parallel operation of modular UPS based on partial power converters according to claim 1 is characterized in that: The expression of battery constant current charging control is: Where: I mload is the actual value of DC load current; I dif,ref is the reference value of the horizontal branch current of the T node; I dif is the actual value of the lateral branch current at the T node; D mc,ref k is the phase shift duty ratio reference value of the dual active full-bridge DC / DC converter; mc,pj , k mc,ij Proportional integral controller PI for constant current charging control of batteries mc The proportional coefficient and integral coefficient of ; s is the Laplace operator; The expression of load constant voltage control is: Where: D mv,refj represents the phase shift duty cycle reference value of the jth MPPC-UPS module, V m1,j represents the actual voltage value of the port where the j-th MPPC-UPS module is connected to the load, k mv,pj and k mv,ij They respectively represent the proportional coefficient and integral coefficient of the load constant voltage control of the j-th MPPC-UPS module.

3. The SOC balancing control method for parallel operation of modular UPS based on partial power converters according to claim 1 is characterized in that: The MPPC-UPS module includes a partial power converter, a backup battery, and a DC load, wherein the partial power converter is composed of a dual active full-bridge DC / DC converter, an inductor L m1 and inductor L m2 The dual active full-bridge DC / DC converter consists of a full-bridge FB m1 、Full bridge FB m2 And high frequency isolation transformer; The positive pole of the DC bus passes through the inductor L m1 Connect the positive pole of the DC load, the negative pole of the DC load is connected to the positive pole of the backup battery, the connection point between the negative pole of the DC load and the positive pole of the backup battery is recorded as the T node, the negative pole of the backup battery is connected to the negative pole of the DC bus; the positive pole of the DC bus passes through the inductor L m1 Connect full bridge FB m1 Positive, full bridge FB m1 The negative pole passes through the inductor L m2 Connected to the T node to form a DC bus, inductor L m1 、Full bridge FB m1 、Inductance L m2 The branch connected in series with the backup battery, at the same time the full bridge FB m1 It also forms a parallel connection relationship with the DC load; full bridge FB m2 The positive electrode passes through the inductor L m2 Connect to the T node, and its negative terminal is connected to the negative terminal of the backup battery.

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